THE TRANSPORTATION OF LIQUIDS
being cleaned. A surface condenser may be placed in the suction pipe of the pump, provided there is a place below it for the condensate pump. It is arranged so that the water flows around the tubes, while the exhaust steam flows through the tubes. Only a small wet vacuum pump is then required to remove the condensate and the air. A better place for it is in the discharge pipe as this gives a greater suction head for the vacuum pump. This is much more costly on account of the high pressure for which it must be designed, but an obstruction in the discharge pipe is by far not so objectionable as one in the suction pipe.
Acid Pumps.—When an acid or other corrosive substance is to be handled by a pump no material should be used that is attacked by the substance. For this reason pumps may be constructed either wholly of brass, bronze, rubber or even stone ware, or wholly of iron or they may be merely bronze fitted, which means that certain working parts such as pistons, rods, pump pistons, etc., are made of bronze or bronze lined. In ordering bronze or brass-fitted pumps it should be clearly specified what parts should be made of bronze or brass. In an all-iron pump the pump cylinder is bored to size and has no lining. The valve seats and stems are made of malleable iron.
If the size permits it in a brass fitted pump the piston rod should be split in the cross head, and the steam piston rod should be made of steel. Brass at the high temperature in the steam cylinder is too soft to wear well.
Table 6 gives a very complete list of substances that may be handled by pumps and the materials of which the pump parts should be constructed.
TABLE 6.—MATERIALS FOR PUMP PARTS FOR HANDLING VARIOUS LIQUIDS
Column 2 Columns 4 and 6 Compositions of
Condition material acid metal
Con. Dil Ex. c. Concentrated Diluted Extremely concentrated AB AI AM BF All bronze All iron Acid metal Brass fitted Cu Sn Pb Sb Al Tensile strength
82 88 5 10 12 2 1
CI. Cast iron
Column 5 E Enameled 90 Aluminum Bronze 10 45,000
valve service HL Hard lead
LB High lead bronze 75 5 20 Light section 19,000
80 5 15 Heavy section 15,000
R Regular valve MM Monel metal
L.O. disc, etc. Large openings No ribs in scat PB RF AL Phosphor bronze Regular fitted Aluminum M H (Fo 85M r mine 13H water) (Ant. lead)
Ball valve Cu Copper
Clapper Valve Pb Lead
Etc. Sb Antimony
SbPb Antimonial lead 90 10 (For acid)
The column numbers refer to the columns on pp. 130-134. For handling substances for which material E is specified, pumps made entirely of rubber would be most suitable. The American Hard Rubber Co., New York, N. Y., is developing such a line, which will include single and duplex direct-acting, steam pumps, power and centrifugal pumps, as well as piping, fittings and valves. Pumps handling foods or medicines must be kept clean and should preferably be all bronze.